Police have arrested two snipers in the northern city of Medellin who they said were planning to assassinate Mr Uribe Velez in the next few days.

Peace talks with the FARC are stalled

Police said the men belonged to the urban militia of Colombia's largest rebel group the FARC, or Revolutionary Armed Forces of Colombia.

If proven to be true, it would be the third reported attempt on the hard-line Mr Uribe Velez, who has made it abundantly clear he will not continue the present government's three-year peace process under the current conditions.

Peace talks have not made any progress, or seem likely to in the near future, despite record levels of violence and kidnapping.

Dead deal

Sources within the FARC, while not admitting to any attempt to kill Mr Uribe Velez, have said his election will bring the tentative peace process to an end and plunge the country into open war.

The FARC have publicly accused Mr Uribe Velez of being in league with their right wing paramilitary enemies.

Last September, four alleged members of the FARC were arrested in a plot to put a suitcase with bibles stuffed with explosives at a favourite meeting place of Mr Uribe Velez in the capital Bogota.

Running for president has always been a risky business in Colombia. During the 1990 presidential campaign, three candidates were assassinated by drugs traffickers and right wing paramilitaries.

Now evidence suggests the Marxist guerrillas will also go to any lengths to ensure a candidate opposed to them doesn't make it to election day.

Again it seems , were behind the plot.

Mr Velez has said that if he wins the presidency he will no longer tolerate guerrilla attacks while peace talks are going on threatening to plunge Colombia into all-out war. Jeremy McDermott reports from Colombia:)